KR20180116356A - Noble metal compound - Google Patents

Abstract

The present invention relates to a process for the preparation of tetraalkylammonium-tetra- or hexahydroxometallates such as tetraethylammonium hexahydroxoplatinate, (N (alkyl) 4) y [M (OH) x] ≪ / RTI >

Description

Noble metal compound

In the course of the deposition of platinum metal onto a base material, e.g., oxide particles, some requirements exist for platinum-containing platinum starting materials.

Which advantageously can be made into a basic solution having a platinum content of about 10% (e.g., 9 to 11%) and is halogen-free or at least halogen-deficient and can contain carbon, hydrogen, oxygen, , And will have the minimum nitrogen content possible to minimize nitrogen oxide emissions. It should also be possible to completely settle as much as possible by changing the pH value.

These conditions are met by tetraalkylammonium tetra- or hexa-hydroxymetalates of the formula (N (alkyl) ₄ ) _y [M (OH) _x ]

M is a metal selected from the group consisting of rhodium, platinum, iridium, or palladium;

Alkyl is an alkyl group having up to 6 carbon atoms;

Y is 1, 2, or 3; And

X is 4 or 6;

Alkyl is especially preferably methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, An alkyl group selected from the group consisting of 2-methylbut-2-yl, neopentyl, n-hexyl, 3-methylpentyl, isohexyl, neohexyl, 2,3, -dimethylbutyl or combinations thereof. The alkyl groups may be the same or different, but are advantageously the same.

In particular, tetraethylammonium hexahydroxyplatinate (N (CH ₂ CH ₃ ) ₄ ) ₂ [Pt (OH) ₆ ] - hereinafter referred to as Pt-TEAH - has proven its value. The compound may be prepared as a solution having the desired platinum concentration. The halogen content (especially chlorine) is adjusted by the chlorine content of the reactants used.

This specifically includes each of the following compounds of the general formula (N (alkyl) ₄ ) _y [M (OH) _x ] wherein alkyl, M and x have the following meanings according to formula

The structure of the hexahydroxy platinate is well defined, while the structure of the other metal hydroxides is not always clearly characterized or even characterized.

For example, in the case of rhodium, whereby the compounds according to the invention, depending, for example, the structure in the case of _{Rh-TEAH [N (CH 2} CH 3) 4] 3 [Rh (OH) 6], [N ( Alkyl) ₄ ] ₃ [Rh (OH) ₆ ].

In the case of palladium, (N _{(alkyl) 4) 2 [Pd (OH} ) 4], but even (N (alkyl) ₄₎ [Pd (OH) ₃ (H ₂ O)] may also be present singly or as a mixture.

In general, the compounds are also (N _{(alkyl) 4) s [M (OH} ) v (H 2 O) w] can be present in the structure, such as a ^uv, where u is the charge of the metal, v = 1 to max W is the coordination number of the metal-v, and s = 1 to maximum uv.

The tetraalkylammonium tetra- or hexa-hydroxymetalates of the above-described compounds, of the formula (N (alkyl) ₄ ) _y [M (OH) _x ] can be reacted with a hydroxy compound of a metal, Can be obtained through the reaction of tetra- or hexa-hydroxy acid of the metal with each tetraalkylammonium hydroxide.

In the case of platinum, hexahydroxyplatinate has rhodium, rhodium hydroxide; Palladium, palladium hydroxide, and the like. These compounds can be precipitated by adding a metal salt to the base and are thus obtained in this way. Suitable bases include alkali metal hydroxides or aqueous solutions thereof, but also optionally tetraalkylammonium hydroxides, such as tetraethylammonium hydroxide in particular. An example of this is the precipitation of palladium hydroxide by adding a solution of palladium nitrate or palladium chloride to a solution of tetraethylammonium hydroxide. Where a minimum possible halogen content is desired, then the nitrate is preferred over the original halide.

Such compounds are not always clearly characterized, and sometimes they may also have aquo-ligands. What is meant herein is, in general, all such compounds having a hydroxy compound of a metal, such as a tetra- or hexa-hydroxy acid thereof, which can also be regarded as a starting compound. Thus, rhodium hydroxide is often described as H ₃ [Rh (OH) ₆ ].

For example, Pt-TEAH-tetraethylammonium hexahydroxyplatinate can be produced by the reaction of hexahydroxyplatinic acid with tetraethylammonium hydroxide optionally in the presence of a reaction medium.

Hydroxy compounds of metals, such as tetra- or hexa-hydroxy acids of each metal, can be produced with various halogen contents, especially chlorine content. Such halogen content is typically less than or equal to 30,000 ppm, or less than or equal to 20,000 ppm, or less than or equal to 15,000 ppm, especially less than or equal to 10,000 ppm, less than or equal to 5,000 ppm, or less than or equal to 1,000 ppm. In particular, the halogen content is a chlorine content, which can be generated in the above-mentioned quantities.

Hexahydroxyplatnic acid can be produced with a variety of halogen contents-in particular, chlorine content. This is generally not more than 30,000 ppm, or not more than 20,000 ppm, or not more than 15,000 ppm, especially not more than 10,000 ppm, not more than 5,000 ppm, or not more than 1,000 ppm, and the halogen content is related to the platinum metal.

Hydroxy compounds of the metal, such as tetra- or hexa-hydroxy acids of each metal or respective tetraalkylammonium hydroxides, are preferentially provided, and it is not important whether each reaction counterpart is added. Thus, a hydroxy compound of a metal such as a tetra- or hexa-hydroxy acid of a desired metal or a solution thereof may be provided, and a tetraalkylammonium hydroxide having a desired alkyl group may be added to the solution as needed, Tetraalkylammonium hydroxide or a solution thereof may be provided and a hydroxy compound of a metal such as a tetra- or hexa-hydroxy acid of the desired metal is added to the solution as needed.

In one embodiment, the addition of the reactants, hexahydroxyplatinate and tetraethylammonium hydroxide is not critical, which may provide tetraethylammonium hydroxide or a solution thereof, followed by addition of hexahydroxyplatinic acid, or Hexahydroxyplatnic acid may even be provided first, after which tetraethylammonium hydroxide or a solution thereof may be added and then reacted with each other.

The reaction may optionally take place in the reaction medium, which can advantageously be a solvent or a solvent. Polar, protic solvents are very suitable.

The reaction medium may be selected from the group consisting of water, one or more alcohols, one or more acids, and mixtures thereof. In particular, the reaction medium may be selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, 1-methylbutanol, 2-methylbutanol, tert-butanol, formic acid, acetic acid, propionic acid and combinations thereof. Water is a particularly suitable reaction medium; In practice, demineralized or distilled water is commonly used in such cases.

The reaction medium is advantageously provided prior to the addition of the reactants. However, it can also be provided at the same time as a single reactant or when two reactants are provided or added as a solution or suspension, for example, as a solution of tetraethylammonium hydroxide.

The reactants are reacted at reaction temperatures which are within a predetermined range for a predetermined reaction time.

In general, a reaction time of 10 minutes to 24 hours, particularly 20 minutes to 12 hours, 30 minutes to 6 hours, 45 minutes to 3 hours, or 45 minutes to 120 minutes, or 50 minutes to 70 minutes is sufficient Do. Approximately one hour of reaction time is generally sufficient.

The reaction time can be from 10 캜 to 100 캜, especially from 15 캜 to 80 캜, or from 20 캜 to 50 캜, or from 20 캜 to 40 캜. Where a reaction medium is used, the maximum reaction temperature is the boiling point of the reaction medium. In practice, temperatures of 20 ° C to 50 ° C have proven useful.

In order to produce the desired tetraalkylammonium tetra- or hexa-hydroxymetalate of the formula (N (alkyl) ₄ ) _y [M (OH) _x ], a hydroxy compound of a metal such as tetra- or hexa- A tetraalkylammonium hydroxide of 0.5 or more, especially 1.7 or more, molar equivalents, per mole of hydroxyacid is used. Hydroxyl compounds of the metal, such as from 0.5 to 17 molar equivalents, from 1.7 molar equivalents to 17 molar equivalents, and especially from 2 molar equivalents to 6 molar equivalents, of tetraalkylammonium hydroxide per mole of tetra- or hexa-hydroxy acid of the metal are useful . If the metal M to be used is palladium, then, in particular, 0.5 to 2 molar equivalents, in particular 1 to 1.7 molar equivalents, of tetraalkylammonium hydroxides are advantageous.

To prepare Pt-TEAH, for example, tetraethylammonium hydroxide is used in an amount of 1.7 molar equivalent or more per 1 mol of hexahydroxyplatinic acid. Tetraethylammonium hydroxides of 1.7 to 17 molar equivalents, in particular 2 to 6 molar equivalents, per mol of hexahydroxyplatinic acid have proven useful.

When a reaction medium is used, the desired product of the formula (N (alkyl) ₄ ) _y [M (OH) _x ] (tetraalkylammonium tetra- or hexa-hydroxymetalates is generated as a solution- , Wherein the concentration of platinum, palladium, rhodium or iridium is between 1 wt% and 15 wt%, especially between 10 wt% and 15 wt%.

If the desired product is Pt-TEAH, where a reaction medium is used, it is generated as a solution, especially an aqueous solution, wherein the platinum concentration is 1 wt% to 15 wt%, especially 10 wt% to 15 wt%.

The tetraalkylammonium tetra- or hexa-hydroxymethalates of formula (N (alkyl) ₄ ) _y [M (OH) _x ] or their formulations are precursors for the production of heterogeneous catalysts For use in a batch, as a precursor product for the preparation of a homogeneous catalyst, or even as a homogeneous catalyst per se. The foregoing is likewise suitable for the production of materials for fuel cells.

Pt-TEAH or its preparation is a precursor for the preparation of, in particular, heterogeneous catalysts (e.g. automotive exhaust catalysts or fuel cells), for use in galvanic baths, as a precursor product for the preparation of homogeneous catalysts, or even as a homogeneous catalyst itself Suitable.

To prepare the heterogeneous catalyst, a solution of a tetraalkylammonium tetra- or hexa-hydroxymetallate of the formula (N (alkyl) ₄ ) _y [M (OH) _x ] Aluminum oxide or silicon dioxide. The metal oxide, i. E. Aluminum oxide or silicon dioxide, is advantageously used in the form of powders or particles.

The tetraalkylammonium tetra- or hexa-hydroxymetallates of the formula (N (alkyl) ₄ ) _y [M (OH) _x ] are then reacted, or chemically reacted, Precipitated and is at least partially deposited on the surface of the substrate, i.e., metal oxide particles. Thus, deposition can occur by precipitation, or even by adsorption.

Under certain desirable conditions, the elemental metal can also be deposited. To produce this, a reducing agent such as hydrogen, hydrazine, or formic acid should be added. This method is particularly noted for the manufacture of materials for fuel cells.

The reaction and precipitation of the metal compound can be achieved by varying the pH value. In this case, a hydroxy compound of each metal, especially a tetrahydroxy or hexahydroxy acid of, for example, a metal (i.e., rhodium, platinum, iridium, or palladium) may be deposited and deposited on the metal oxide particles.

In a further processing step, the elemental metal can be produced on the particles of the substrate material through calcination of the metal oxide particles, whereby a metal compound is deposited thereon.

In one particular embodiment, for the purpose of producing a heterogeneous catalyst, a solution of Pt-TEAH is mixed with a base material such as aluminum oxide or silicon dioxide used in the form of a metal oxide, for example, Can be mixed.

The Pt-TEAH is then reacted, i.e., chemically reacted, whereupon a platinum compound precipitates and is at least partially deposited on the surface of the particles of the substrate material, i. E. Metal oxide particles.

The reaction and precipitation of the platinum compound can be achieved by varying the pH value. In this case, the hexahydroxyplatinum acid can be deposited and deposited on the metal oxide particles in particular.

In a further processing step, the elemental platinum is produced on the particles of the base material through calcination of the metal oxide particles, whereby a metal compound is deposited thereon.

Metal compounds, particularly platinum compounds, as well as base compounds deposited thereon, as well as metal compounds, in particular platinum compounds whose platinum compounds have been converted to elemental metals, in particular platinum compounds, by calcination, can be used to prepare automotive exhaust catalysts .

To this end, a coating suspension (also referred to as a washcoat) is produced, which contains the substrate material. As described above, it generally comprises a metal oxide, especially aluminum oxide or silicon dioxide.

By means of the coating suspension, the inner wall of the flow channel of the support required for the production of an automobile exhaust catalyst is coated, for example, in a known manner as described, for example, in EP-A1-1273344.

The support is usually fabricated from metal or ceramic and can be designed as a flow-through honeycomb body or a wall-flow filter. This is a cylindrical body generally having a circumferential outer surface and two oppositely disposed end surfaces, wherein the supporting channel is traversed by a working flow channel between the two end surfaces.

A catalyst body having a round, oval, or triangular cross section is widely used. In most cases, the flow channels have a square cross section and are arranged in a rigid pattern on the entire cross section of the catalyst body. Depending on the field of application, the tube or cell density of the flow tube has varied from 10 to 250 cm ^-2 in most cases. Recently, a catalyst support having a cell density of about 62 cm & lt ^; " ^{2 &} gt ^; is still often used for exhaust gas cleaning. In the case of a well-flow filter, it is cross-hermetically sealed so that the through-flowing exhaust gas stream is transferred through the pores to the walls forming the flow channels.

After application of the coating suspension, the coated honeycomb body is subjected to further processing steps as needed, dried and finally calcined. If a platinum compound employs a substrate material deposited thereon, then conversion to elemental metal takes place and coating of the support is followed in the course of the calcination step.

If the substrate material to be calcined after the deposition of the platinum compound (for example, platinum on the aluminum oxide-based material) has already been used to prepare a coating suspension, the elemental platinum is already present on the substrate material prior to coating of the support , The calcination of the coated support has no effect with respect to the conversion of the deposited platinum compound.

Example

Example 1: Preparation of Pt-TEAH (tetraethylammonium hexahydroxyplatinate)

In a reactor having a capacity of 5 liters, 758 g of demineralized water was provided and 1.47 kg of a tetraethylammonium hydroxide aqueous solution at a concentration of 35 wt% was added, which corresponds to approximately 2 moles per mole of platinum.

With stirring, 894.74 g of hexahydroxyplatonic acid with a platinum content of 38 g was then added. This was then stirred at a temperature of approximately 20 ° C to 30 ° C for one hour, where a yellow-orange solution was generated, which was filtered on a G4 glass frit and analyzed.

The solution had a noble metal content of 10.9 wt% platinum and a pH value of 13.9.

The product was also examined using capillary electrophoresis and the results are shown in FIG. The composition is characteristic of the compound, Pt-TEAH. The main peak corresponds to that of the [Pt (OH) ₆ ] ^2- complex. The smaller second peak corresponds to an additional anionic Pt complex of the unknown composition, [Pt (OH) _{6 - x} (NEt) _x ] ^2-x (x = 1-2). The percentage distribution of the two major components may vary depending on the manufacturing method and the quality of the reactants.

Example 2: Preparation of Rh-TEAH

13.5 g of rhodium hydroxide (RhOH ₃ ) was suspended in 10 g of water, and a solution of 61.594 g of tetraethylammonium hydroxide in a concentration of 35 wt% was added in one portion and stirred at a temperature of 22 ° C for 1 hour, A brown solution occurred after approximately 10 minutes, which was filtered through a G4 glass frit and analyzed.

The solution had a noble metal content of 10 wt% and a pH value of approximately 10 (determined using a universal test strip).

Example 3: Preparation of Pd-TEAH

Preparation of hydroxides

A solution of 866 g of tetraethylammonium hydroxide in a concentration of 35 wt% was provided and approximately 540 g of a palladium nitrate solution with a content of 130 g of palladium over 30 minutes was added dropwise until the pH value reached 3.6 to 3.7; The exact amount of solution depends on the palladium content and can vary accordingly. During the addition process, the reaction heat generated caused heating to 40 ° C.

It was stirred overnight for approximately 18 hours and filtered through a G4 glass frit. The solids-precipitated hydroxides obtained were washed with demineralized water until the filtrate became dark brown and dried overnight in vacuo.

Preparation of Pd-TEAH

A 1.0 molar equivalent of tetraethylammonium hydroxide solution was then provided at a concentration of 35 wt%, and the dried filtrate was added and stirred at a temperature of 23 DEG C for 1 hour. It was then filtered over G4 glass frit and dried.

The yield of (N (alkyl) ₄ ) _y [M (OH) _x ] was 90% based on the palladium used.

The solution had a noble metal content of 10.2 wt% and a pH value of approximately 11 (determined using a universal test strip).

Example 4: Preparation of Pt-TPAH (tetrapropylammonium hexahydroxyplatinate, alkyl = n-propyl)

An aqueous solution of tetrapropylammonium hydroxide (40 wt%) was used, and an aqueous solution containing 31.92 wt% hexahydroxyplatin acid was provided, which was stirred at 20 ° C to 25 ° C for 180 minutes and then warmed to 50 ° C; An additional 5 mL of tetrapropylammonium hydroxide solution was added, allowed to stand overnight (approximately 18 hours), filtered on G4 glass frit and the same procedure as in Example 1 except that it was centrifuged for 15 minutes. The resulting clear tetrapropylammonium hexahydroxyplatinate solution had a platinum content of 9.08%.

Example 5: Preparation of Pt-TBAH (tetrabutylammonium hexahydroxyplatinate: alkyl = n-butyl)

Frozen tetrabutylammonium hydroxide * 30 H ₂ 0 was used; The procedure was the same as in Example 4 except that an aqueous solution containing 39.3 wt% hexahydroxyplatnic acid was provided, stirred at 20 ° C to 25 ° C overnight (approximately 18 hours) and centrifuged for 15 minutes. The thus obtained transparent tetrabutylammonium hexahydroxyplatinate solution exhibited a deep yellow color.

The solution had a noble metal content of 9.8 wt% and a pH value of approximately 10 (determined using a universal test strip).

Example 6: Preparation of a coating suspension for the production of a heterogeneous catalyst

45 g of aluminum oxide and 16 g of zeolite (zeolite-HSZ-0940NHA, manufactured by Tosoh) were suspended in water and stirred for 15 minutes. The pH value was then adjusted to 10 through the addition of tetraethylammonium hydroxide, then 0.81 g of dissolved platinum in the form of a soluble platinum compound was added and stirred for 15 minutes. Then 0.54 g of palladium in the form of palladium nitrate in water was added and stirred again for 15 minutes. The pH value was then adjusted to a value of 5 with acetic acid, followed by stirring for 5 minutes. Then, the remaining noble metal content in the water was determined.

Comparative Example 6a: Platinum was added in the form of an ethanolamine-hexahydroxyplatinate solution in water. After the end of the experiment, it was determined that 10% of the initial palladium concentration and 20% of the initial palladium concentration were present in the solute. The remaining noble metal was precipitated on the support (aluminum oxide and zeolite) provided.

Example 6b: Platinum was added in the form of an aqueous solution of tetraethylammonium hexahydroxyplatinate (Pt-TEAH). After the end of the experiment, no more platinum was present in the solution and only 0.8% of the initial palladium concentration was determined to remain in the solution. The remaining noble metal was precipitated on the support (aluminum oxide and zeolite) provided.

Claims (22)

Tetraalkylammonium tetra- or hexa-hydroxymetalates of the formula (N (alkyl) ₄ ) _y [M (OH) _x ]
Wherein M is a metal selected from the group consisting of rhodium, platinum, or palladium;
Alkyl is an alkyl group having up to 6 carbon atoms;
Y is 1, 2, or 3; And
X is 4 or 6; The compounds tetraethylammonium hexahydroxyplatinate (Pt-TEAH), (N (CH ₂ CH ₃ ) ₄ ) ₂ [Pt (OH) ₆ ]. The process of claim 1 wherein the alkyl is selected from the group consisting of ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, sec-pentyl, Methylbut-2-yl, neopentyl, n-hexyl, 3-methylpentyl, isohexyl, neohexyl, 2,3, -dimethylbutyl, or combinations thereof. Tetraalkylammonium tetra- or hexa-hydroxymetalates which are alkyl groups. 4. Tetraalkylammonium tetra- or hexa-hydroxymetalate according to any one of claims 1 to 3, wherein M is palladium and X = 4 or M is rhodium or platinum and X = 6. A tetraalkylammonium tetra- or hexa-hydroxy-substituted tetraalkylammonium tetra- or tetraalkylammonium tetra- or tetraalkylammonium tetra- or tetraalkylammonium-tetraalkylammonium tetra- Metallate. A process for the production of tetraalkylammonium tetra- or hexa-hydroxymetallates by reaction of a hydroxy compound of a metal selected from the group consisting of rhodium, platinum, or palladium with a tetraalkylammonium hydroxide, optionally in the presence of a reaction medium. 7. The process according to claim 6, wherein a tetraalkylammonium hydroxide or a solution thereof is provided and the hydroxy compound of the metal such as tetra- or hexa-hydroxy acid is added and reacted for a predetermined reaction time at a reaction temperature within a predetermined range. 7. The process according to claim 6, wherein a hydroxy compound of a metal such as tetra- or hexa-hydroxy acid is provided and a tetraalkylammonium hydroxide or a solution thereof is added and reacted for a predetermined reaction time at a reaction temperature within a predetermined range. 9. A process according to any one of claims 6 to 8, wherein the reaction medium is provided prior to the addition of the reactants. 10. The process according to any one of claims 6 to 9, wherein the reaction medium is a polar, protic solvent. 11. A process according to any one of claims 6 to 10, wherein the reaction medium is selected from the group consisting of water, one or more alcohols, one or more acids, and mixtures thereof. 11. The process according to any one of claims 6 to 10, wherein the reaction medium is selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, 1-methylbutanol, 2- methylbutanol, And a solvent selected from the group consisting of combinations thereof. Process according to any one of claims 6 to 12, characterized in that the process is carried out at a temperature of from 10 캜 to 100 캜, especially from 15 캜 to 80 캜, or from 20 캜 to 50 캜, or from 20 캜 to 40 캜 . 14. A process as claimed in any one of claims 6 to 13, characterized in that the hydroxy compound of the metal, for example 0.5 to 17 or 1.7 to 17, especially 2 to 6, molar equivalent of tetra- or hexa-hydroxy acid per mole of tetra- or hexa- Ethylammonium hydroxide is used. (Tetraethylammonium hexahydroxyplatinate (Pt-TEAH), (N (CH ₂ CH ₃ ) ₄ (tetraethylammonium tetra- or tetraethylammonium hexafluorophosphate) having a platinum concentration of 1 wt% to 15 wt% ) ₂ [Pt (OH) ₆ ]. As a precursor product for the preparation of a homogeneous catalyst for use in a galvanic bath, or as a homogeneous catalyst, as a precursor for the preparation of a catalyst for use in a fuel cell, a heterogeneous catalyst, an automobile exhaust catalyst, tetraalkylammonium-or hexa-hydroxy metal acrylate, particularly, tetraethylammonium hexafluoro-hydroxy platinum salt (Pt-TEAH), (N (CH 2 CH 3) 4) 2 [Pt (OH) 6] - or a Use of aqueous formulation. A process for the preparation of an automotive exhaust catalyst comprising the steps of: contacting a tetraalkylammonium tetra- or hexa-hydroxymethalate according to one of claims 1 to 5, in particular tetraethylammonium hexahydroxyplatinate (Pt-TEAH) (N (CH ₂ CH ₃ ) ₄ ) ₂ [Pt (OH) ₆ ] - and at least one base material; By reaction of tetraalkylammonium tetra- or hexa-hydroxymethalate, a metal in the form of a hydroxy compound such as tetra- or hexa-hydroxyacid is precipitated on the base material and the catalyst support is entirely or Partially coated; Wherein the hexahydroxyplatinum acid applied to the substrate material is calcined before or after the coating of the catalyst support. 18. The method according to claim 17, wherein the base material is a metal oxide, especially aluminum oxide or silicon dioxide. 19. The method according to claim 17 or 18, wherein the catalyst support is a wall-flow filter or a flow-through honeycomb body. 20. The process according to any one of claims 17 to 19, wherein the reaction of the tetraalkylammonium tetra- or hexa-hydroxymetalate is effected by varying the pH value. 21. The process according to any one of claims 17 to 20, wherein the metal is platinum precipitated as hexahydroxyplatinum acid. 22. A process according to any one of claims 17 to 21, wherein the reaction of tetraethylammonium hexahydroxyplatinate (Pt-TEAH) to precipitate hexahydroxyplatinum acid on the substrate material is effected by changing the pH value Way.

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